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JAVA认证历年真题:SCJP考试真题和解析3

发表时间:2014/4/21 9:54:46 来源:互联网 点击关注微信:关注中大网校微信
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例题7:

True or False: Readers have methods that can read and return floats and doubles.

A. Ture

B. False

解答:B

点评: Reader/Writer只处理Unicode字符的输入输出。float和double可以通过stream进行I/O.

例题8:

What does the following paint() method draw?

1. public void paint(Graphics g) {

2. g.drawString(“Any question”, 10, 0);

3. }

A. The string “Any question?”, with its top-left corner at 10,0

B. A little squiggle coming down from the top of the component.

解答:B

点评:drawString(String str, int x, int y)方法是使用当前的颜色和字符,将str的内容显示出来,并且最左的字符的基线从(x,y)开始。在本题中,y=0,所以基线位于最顶端。我们只能看到下行字母的一部分,即字母‘y’、‘q’的下半部分。

例题9:

What happens when you try to compile and run the following application? Choose all correct options.

1. public class Z {

2. public static void main(String[] args) {

3. new Z();

4. }

5.

6. Z() {

7. Z alias1 = this;

8. Z alias2 = this;

9. synchronized(alias1) {

10. try {

11. alias2.wait();

12. System.out.println(“DONE WAITING”);

13. }

14. catch (InterruptedException e) {

15. System.out.println(“INTERR

UPTED”);

16. }

17. catch (Exception e) {

18. System.out.println(“OTHER EXCEPTION”);

19. }

20. finally {

21. System.out.println

(“FINALLY”);

22. }

23. }

24. System.out.println(“ALL DONE”);

25. }

26. }

A. The application compiles but doesn't print anything.

B. The application compiles and print “DONE WAITING”

C. The application compiles and print “FINALLY”

D. The application compiles and print “ALL DONE”

E. The application compiles and print “INTERRUPTED”

解答:A

点评:在Java中,每一个对象都有锁。任何时候,该锁都至多由一个线程控制。由于alias1与alias2指向同一对象Z,在执行第11行前,线程拥有对象Z的锁。在执行完第11行以后,该线程释放了对象Z的锁,进入等待池。但此后没有线程调用对象Z的notify()和notifyAll()方法,所以该进程一直处于等待状态,没有输出

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